Engine brake device for a commercial vehicle

ABSTRACT

An internal combustion engine includes an intake valve for controlling a cylinder intake port; an exhaust valve for controlling a cylinder exhaust port; first and second valve lifters coupled to the intake and exhaust valves, respectively, for cyclically opening and closing the intake and exhaust valves during normal engine operation; and an actuating device for contacting the exhaust valve and for operating the exhaust valve independently from the second valve lifter. The actuating device has a withdrawn position and a valve-contacting position. In the withdrawn position the actuating device is out of contact with the exhaust valve and in the valve-contacting position the actuating device is in contact with the exhaust valve. There is further provided an electromagnetically-operating setting device having an inoperative position assumed for a normal engine operation and an operative position assumed for an engine-braking operation. The actuating device is coupled to the electromagnetically-operating setting device such that in the inoperative position of the electromagnetically-operating setting device the actuating device is in the withdrawn position and in the operative position of the electromagnetically-operating setting device the actuating device is in the valve-contacting position. The electromagnetically-operating setting device further has a mechanism for operating the actuating device to open and close the exhaust valve when the actuating device is in the valve-contacting position.

BACKGROUND OF THE INVENTION

In exhaust gas turbocharger engines used in commercial vehicles, theincreasing level of charge decreases the braking performance related touseful effect. Contemporary systems often can no longer meet the legalrequirements. Auxiliary systems, such as retarder brakes, are extremelycostly. The braking performance made possible by the use of an exhaustgate is limited.

SUMMARY OF THE INVENTION

To further increase the engine braking performance, an engine brakingdevice for an internal combustion engine, particularly for a dieselengine, is provided in accordance with the invention, the device havingan actuatable blocking element in the exhaust gas line and an actuatingmeans that respectively acts on at least one discharge valve of acylinder and is in operational connection with anelectromagnetically-operating setting device.

The provision of this device makes it possible to actuate the dischargevalve at least once during the compression phase of the engine, inaddition to the usual opening times of the discharge valve, in order toadditionally influence the exhaust gate. This additional opening iseffected at least shortly before the end of the compression phase, sothe compressed cylinder contents are pushed out into the exhaust gasline blocked by the exhaust gate and, after the exhaust valve closes andthe upper dead center is exceeded, are no longer available forretroactively affecting the piston. In addition, the discharge valve canbe opened briefly, by way of the electromagnetic setting device, at thestart of the compression stroke, so that the gas blocked in the exhaustgas line by the exhaust gate flows into the cylinder due to theoverpressure, necessitating additional compression work that has abraking effect on the vehicle. The particular advantage of the enginebraking device of the invention in comparison to conventionalmechanically, hydraulically or pneumatically actuated braking devices ofthis type is that "individual actuation" is possible with the use of acorresponding control device. Thus, it is possible, for example, tocreate a stepped braking effect by way of this exhaust gas brake in thatnot all cylinders are affected when the braking process is initiated;only one or a few of the cylinders is or are initially actuated. Anopening and closing of the discharge valves that is optimal with respectto the braking moment can be effected with this type of actuation,preferably electronic actuation, of the individualelectromagnetically-operating setting units as a function of rpm duringthe compression stroke in braking operation.

A further advantage of the engine braking device of the invention liesin the reduction of components compared to conventional braking systems;as a result, the electromagnetically-operating setting device can bedisposed in the cylinder head of the engine, for example laterally nextto or above the valves.

In an advantageous embodiment of the invention, it is provided that theelectromagnetic setting device is formed by a setting block in which anarmature is guided which is in operational connection with the actuatingmeans, the armature also being connected to two spring elements actingcounter to one another, the armature further being allocated at leastone magnetic coil as an opening element and at least one magnetic coilas a closing element. To activate the setting unit, the armature isbrought into the closing position by the closing magnet. The settingunit is subsequently brought into engagement with the aid of themagnetic coil, by way of the valve lifter, or the lower spring isprestressed with the aid of the additional coil and the prestressingarmature. To open the valve, the prestressing magnet is shut off, sothat the armature moves to the oppositely-located opening magnet and istaken over by this magnet. The impact speed of the armature against theopening magnet is determined by the other spring and by thecharacteristic of the current path of the opening magnet, by means ofwhich the armature is held during the short opening phase of thedischarge valve. The valve is closed by the shutoff of the openingmagnet and simultaneous activation of the closing magnet.

This system permits activation of the setting device through thestimulation of armature oscillation at the natural system frequency andsubsequent holding of the armature by the closing magnet, withsimultaneous prestressing of the spring, and overall lifting of thesetting block by the setting

means, for example an additional magnet, thus effecting the contact ofthe actuating means with the tappet (shaft) of the discharge valve. Theadvantage of this combination is that, in the shut-off, currentlessstate, the discharge valve can operate freely in a normal operatingcycle, and its function is not impaired by contact with the actuatingmeans of the braking device, so even an incorrect setting of the workcycle of the actuating means has no effect on the discharge valve, andcannot lead to a reduction in engine performance during the compressionphase and work phase of the relevant cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail below in conjunction with schematicdrawings of embodiments. Shown are in:

FIG. 1 a partial section through a cylinder head of an engine,

FIG. 2 a top view of a four-valve engine having a setting device,

FIG. 3 a section of a first embodiment of the setting means,

FIG. 4 a different arrangement of the electromagnetic setting means withrespect to the actuating means,

FIG. 5 another embodiment of the electromagnetic setting means.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The section through the cylinder head of a diesel engine shown in FIG. 1illustrates the intake conduit 1, the associated intake valve 2, thedischarge (exhaust) valve 3 and the discharge conduit 4, which, togetherwith the discharge conduits of the other cylinders, terminates in theexhaust gas line, in which an exhaust valve (gate or flap) is disposedas an actuatable blocking (shut-off) element. During normal operation,the intake valve 2 and the discharge valve 3 are actuated by way of thevalve lifters 5 and 6.

An actuating means 7 in the form of a two-armed valve lifter isassociated with the discharge valve 3, with the short arm 8 beingassociated with the shaft 3a of the discharge valve 3 to be actuated andthe long arm 9 being in operational connection with an electromagneticsetting device 10.

The top view according to FIG. 2, which is derived from FIG. 1, shows apossible arrangement for a four-valve engine having two intake valves 2and two discharge valves 3.1 and 3.2. It can be seen from the top viewthat the actuating means 7 only acts on the discharge valve 3.1; theshort arm 8 in this instance is forked, and extends around the free endof the associated arm of the valve lifter 6. Consequently, the dischargevalve 3.1 can be actuated by way of the setting device 10, independentlyof the normal working rhythm, during the compression phase.

FIG. 3 shows a sectional view of a first embodiment for theelectromagnetically-operating setting device 10. This device has atappet 11 that is connected to an armature 12 and whose free end 13rests against the end of the long arm 9 of the actuating means 7. Theactuating means is typically provided in these regions with a settingscrew 14 (FIG. 1), by way of which the work cycle can be set precisely.The actuating means 7 remains in contact with the tappet 11 by means ofa restoring spring, not shown in detail here, that acts on the actuatingmeans 7.

The armature 12 is connected to two springs 15 and 16, which act counterto one another and by means of which it is held in a predeterminedcentral position. A magnetic coil 17 serving as an opening element onthe side of the spring 15 is further associated with the armature 12, asis a magnetic coil 18 serving as a closing element on the side of thespring 16. To adhere to the oscillator principle, a prestressingarmature 20 is associated with the setting block 19 that holds thesprings 15 and 16 and the magnetic coils 17 and 18; this armature can beactivated by an additional coil 21.

The necessary forces are made available by activating the magnet 18 andfor prestressing the spring 16 by activating the magnet 21. In order toopen the discharge valve 3 by way of the actuating means 7, the magnet18 is shut off and the oppositely-located magnet 17 is turned on, sothat the armature 12 comes into contact with the magnetic coil 17 in theend position of the armature, thereby opening the discharge valve 3. Theimpact speed of the armature against the magnet 17 is delayed by thespring 15.

The closing of the discharge valve 3 is effected by the shutoff of themagnet 17 and activation of the magnet 18.

The actuation of the individual magnets is effected by way of anelectronic control as a function of rpm; this control only permits anopening of the discharge valve at predeterminable times during thecompression phase, preferably at the beginning and end of thecompression phase.

Whereas the arrangement according to FIG. 1 includes the electromagneticsetting device in an embodiment in which the tappet 11 operates as apressure tappet, the embodiment illustrated in FIG. 4 is designed suchthat the tappet rod connected to the armature 12 acts as a towing bar.However, the design and function correspond to FIG. 3, the differencebeing that the association of the individual magnetic coils and thefunctional procedure is reversed with respect to the armature 12, or thearrangement is such that the tappet 11 is guided through theprestressing armature 20 and the opening 22 in the cover plate 23 of thesetting block 19.

The embodiment shown in FIG. 5 is essentially configured like theembodiment according to FIG. 3, so the same reference numerals have beenused for identical structural and functional elements. The additionalprestressing coil 21 and the associated prestressing armature 20 are notincluded in this embodiment, but can be embodied in the same manner. Theembodiment according to FIG. 5 differs from the embodiment according toFIG. 3 in that a base plate 24 is provided, in which a magnetic coil 26is disposed. Because the actuating means 7 configured as a valve lifterutilizes its own restoring spring, the long arm 9 always rests againstthe free end 13 of the tappet 11. The air gap 27 between the base plate24 and the end of the setting block 19 facing the base plate isdimensioned such that, in the currentless state, the short arm 8 of theactuating means 7 is not in contact with the discharge valve, so thatthe free tappet clearance is not impaired during normal operation. Ifthe engine is to be driven with an engine brake, the magnet 26 isactivated, so that the setting block 19 is lifted in its entirety froman inoperative position (shown in FIG. 5) to an operative position inwhich the air gap 27 disappears and the setting block 19 abuts the baseplate 24. As a result, the actuating means 7 comes into contact with thedischarge valve 3 without opening it, because the armature 12 is held bythe closing coil 18. If the setting device 10 is activated by way of theelectronic regulating device by an energization of coils 17, 18 asdescribed in FIG. 3, so that the armature oscillates in theabove-described manner, the discharge valve 3 can now open in thepredetermined rhythm toward the end, but also at the beginning, of thecompression phase of the associated cylinder.

We claim:
 1. An internal combustion engine comprising(a) an intake valvefor controlling a cylinder intake port; (b) an exhaust valve forcontrolling a cylinder exhaust port; (c) first and second valve lifterscoupled to said intake and exhaust valves, respectively, for cyclicallyopening and closing said intake and exhaust valves during normal engineoperation; (d) an actuating device for contacting said exhaust valve andfor operating said exhaust valve independently from said second valvelifter; said actuating device having a withdrawn position and avalve-contacting position; in said withdrawn position said actuatingdevice being out of contact with said exhaust valve and in saidvalve-contacting position said actuating device being in contact withsaid exhaust valve; and (e) an electromagnetically-operating settingdevice having an inoperative position assumed for a normal engineoperation and an operative position assumed for an engine-brakingoperation; said actuating device being coupled to saidelectromagnetically-operating setting device such that in saidinoperative position of said electromagnetically-operating settingdevice said actuating device is in said withdrawn position and in saidoperative position of said electromagnetically-operating setting devicesaid actuating device is in said valve-contacting position; saidelectromagnetically-operating setting device further comprising meansfor operating said actuating device to open and close said exhaust valvewhen said actuating device is in said valve-contacting position.
 2. Theinternal combustion engine as defined in claim 1, wherein said actuatingdevice comprises a pivotal lever having a first arm cooperating withsaid electromagnetically-operating setting device and a second armcooperating with said exhaust valve; said first arm being longer thansaid second arm.
 3. The internal combustion engine as defined in claim2, wherein said second arm has a forked portion straddling an endportion of said second valve lifter.
 4. An internal combustion enginecomprising(a) an intake valve for controlling a cylinder intake port;(b) an exhaust valve for controlling a cylinder exhaust port; (c) firstand second valve lifters coupled to said intake and exhaust valves,respectively, for cyclically opening and closing said intake and exhaustvalves during normal engine operation; (d) an actuating device forcontacting said exhaust valve and for opening and closing said exhaustvalve independently from said second valve lifter; said actuating devicehaving a withdrawn position and a valve-contacting position; in saidwithdrawn position said actuating device being out of contact with saidexhaust valve and in said valve-contacting position said actuatingdevice being in contact with said exhaust valve; and (e) anelectromagnetically-operating setting device comprising(1) a movablesetting block having an inoperative position assumed for a normal engineoperation and an operative position assumed for an engine-brakingoperation; (2) an armature disposed in said setting block; said armaturebeing displaceable relative to said setting block into a valve-openingand into a valve-closing position and further being arranged to move inunison with said setting block during displacements of said settingblock; said armature being in contact with said actuating device; (3)first electromagnetic means for moving said setting block between saidinoperative and operative positions for moving said actuating devicebetween said withdrawn and valve-contacting positions, respectively; and(4) second electromagnetic means for moving said armature relative tosaid setting block between said valve-opening and valve-closingpositions when said setting block is in said operative position.
 5. Theinternal combustion engine as defined in claim 4, wherein said firstelectromagnetic means comprises an electromagnet.
 6. The internalcombustion engine as defined in claim 4, wherein said secondelectromagnetic means comprises a first electromagnet moving, whenenergized, said armature into said valve-opening position and a secondelectromagnet moving, when energized, said armature into saidvalve-closing position.